Analysis of an EHF aplanatic zoned dielectric lens antenna

Zoned dielectric lenses, designed for wide-angle scanning characteristics, are serious contenders to reflector systems for multiple-beam communications and radar applications at EHF frequencies. An analysis is presented in which the zoned lens is approximated by an ideally thin spherical shell (phase transformer) in evaluating the phase aberrations in its aperture plane which are caused by off-axis scanning and deviations from the design frequency. Those results are used to produce a set of universal curves which predict the decrease in directive gain of the lens as a function of scan angle and frequency. Gain and radiation pattern measurements on a zoned dielectric lens show agreement with these predictions and with ray-tracing and geometric optics calculations. This study establishes the validity of the spherical shell analysis as a means for rapid estimation of lens parameters for specific system requirements.